The present invention relates to an apparatus for measuring the relative speed and direction of air moving past an ultrasonic sensing probe. In particular, the present invention comprises a wind vector and velocity measuring apparatus utilizing variations in the propagation time of ultrasonic waves moving from a transmitting transducer means to a plurality of spatially positioned receiving transducer elements.
An aircraft in flight is normally moving so that air will be flowing past the aircraft or moving relative to the aircraft. In order to exercise optimum control over the aircraft itself, or over operations associated with the aircraft when in flight, it is necessary to know the manner in which air is moving past the aircraft. By measuring the air movement, it is then possible to obtain a measure of the forces that are being exerted on the aircraft.
The air movement relative to the aircraft is most conveniently considered in three dimensions; related to the aircraft itself, the directions being along a primary or forward and reverse axis of the aircraft, a vertical axis extending up and down at a right angle to the primary axis of the aircraft, and a horizontal axis extending left and right at a right angle to the primary axis of the aircraft.
Air movement sensing probes have been utilized with aircraft in the past but such probes have not produced the degree of accuracy necessary for modern flight sensing and control purposes.
Ultrasonic measuring devices have been utilized heretofor measuring liquid and gaseous flows. In addition, ultrasonic anemometers have been built but such apparatus heretofore known has not been suitable or practical for use in aircraft installations where factors of size, weight and accuracy must be optimized.
Representative ultrasonic anemometer type apparatus heretofore known will be found in the following identified references:
"A Continuous-Wave Sonic Anemometer-Thermometer," J. C. Kaimal and J. A. Businger (manuscript received Mar. 5, 1962) (pp. 156-167) PA1 "Deriving Power Spectra from a Three-Component Sonic Anemometer," J. C. Kaimal, J. C. Wyngaard and D. A. Haugen, October, 1968. (pp. 827-837) PA1 "Improvements and Refinements on a Pulse Type Sonic Anemometer," Arthur Bisberg, Arthur Papas, and David J. Beaubien. (pp. 1-50) PA1 "Wind Speeds as Measured by Cup and Sonic Anemometers and Influenced by Tower Structure," Yutaka Izumi and Morton L. Barad, December 1970. (pp. 851-856)